Thermostatically actuated automatic switch



Feb. 27, 1940. w, SATrLER 2,191,588

THERMOS' IATICALLY ACTUATED AUTOMATIC SWITCH Filed Sept. 14, 1937 s Sheets-Sheet 1 INVENT OR. W12 (11m {27232 1 Feb. 27, 1940. w. SATTLER 2,191,588

THERMOSTATICALLY ACTUATED AUTOMATIC SWITCH i iled Sept'. 14, 1937 3 Sheets-Sheet 2 4 IN VENTOR.

Feb. 27, 1940. w. 'SATTLER 2,191,588

THERMOSTATICALPY ACTUATED AUTOMATIC SWITCH Filed Sept. 14. 1937 3 Sheets-Sheet 3 P ,A l

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.7 INVENTOR.

7 W/44ATTORNEK Patented-Feb. 21, 1940 2,191,588

7 UNITED ss ATes PATENT OFFICE 2,1915 f g j THERMOSTATICALLY ACTUATED su'rom'rrc swrrcn Application September 1 4, 1937, Serial No. 163,714

In Germany September 22, 1936 4Glaims. (or. 200-416) I V My inventionrelates to thermostatically actutheless should be capable of fully safeguarding ated automatic switches, principally for opening the circuit in which it is placed. It is necessary an electric circuit in case of. overload or short above all that with the use of a thermostat as a circuit. releasing element, the opening of the contacts a For thermostatically releasing automatic occurs quickly, which is particularly important in 5 switches, aside from making use of heated wires case of'a short circuit. The present invention or heated rods which change their length when solves this problem in a simple manner by fixing heated, bimetallic strips are mostly used which one end of the spring which carries one contact, bend or buckle, as the case may be, when the and one end of the strip-shaped bimetallic spring given excess current heats these strips either which carries the second contact in two different 10 directly or indirectly above a given temperature. planes spaced a considerable distance apart. The This motion of the bimetallic strip is utilized for two springs may extend either parallel to or at releasing the switch mechanism. Most of the aran angle toward one another. At the normal rangements of this type known in the prior art closing of the switch, the free ends of these two 16 are of complicated construction, especially in the springs are latched together so that when the switch mechanism, and require a comparatively bimetallic strip is deformed in its response to an large amount of space. In some cases, the deoverload, the two springs are distorted first tosigner is limited to the use of quick-acting switch gether in the same direction whereby the latch mechanisms, because only this type of mechanism between the two strips is disengaged and the two 20 produces the high opening speed necessary for contact springs fly apart and thus open the cir- 20 interrupting currents incident to heavy loads or cuit. The manner in which this occurs will be to short circuits. described laterin .detail with reference to the In electric installations which are operated at a drawings. very low voltage, for instance such as operate The arrangement of such a thermostatically within about forty volts, also very heavy currents operated automatic switch according to the in- M are likely to occur, but in these installations the vention afiords a particularly simple and con danger of arc formations during the interruption densed arrangement of the switch elements and does not exist to such an extent as for instance therefore fulfills the requirement made when in higher voltage installations. While in such these switches are used for the purposes stated lowvoltage-installations the possibility exists to hereinbefore. M

construct the automatic switch in a simpler It is further necessary in switches of this type form, the prior art has in such cases almost exthat the resetting device, if one is used in the clusively resorted to fuses which are renewed switch, be arranged in such manner that it does after have 01109 responded. not interfere with the free operation of. the cut It is undesirable, however, in electric installao t mechanism. My invention solves also this {m tions which are used for instance in automobiles, problem of a trip-free mechanism in a very simaircraft, radio installations, or for similar purple manner.

poses, and which are operated within the low My invention is illustrated in the accompanyvoltagerange above-mentioned, to be compelled, ing drawings in which;

t r th us ha responded. to ex ha t Figures 1 and 2; 3, 4 and 5 respectivelyshow M burnt-out fuse with a new one. This might be two different modifications of the switch indangerous for instance in aircraft, in case ariimvolving t a feature according t my 'p rt t circuit is p d n this-manner, because vention, all of these figures showing the switch of the long time which it takes to make this in longitudinal sectional elevation.

. Figure 1a shows the spring 1' in Figures land 2 change. r

- The present invention therefore proposes to i end l vati empl y or such pu p s a thermostatically op- Figures '6, '7 and 8 illustrate another embodierating automatic switch, which, howeven/with ment in" two longitudinal sections representing the necessary changein design, may also be used the contact opening and the contact closing pofor interrupting circuits operated at higher voltsition, and in a front view, respectively.

ages. Figure 9 indicates amodification of theshape In the design for automatic cut-out switchesto and arrangement of the cooperating contact be used in low voltage plants, it is necessary that springs; and p a the switch be constructed so that it occupies a Figures 1011,10?) and 1111,11?) show two groups very small space and weight, but that it neverof variants serving forjadjusting a switch aclating material, the bimetallic strip c and the contact spring d. The latter is onset at its end towardsthe'strip c and-carries the contact I at its end which cooperates withv the contact e mounted at the end of bimetallic strip 0. Contact spring (2 carries further an extension 1 made of insulating material which extends in the direction of the general longitudinal'axls of this,

spring and which carries at its end a small latch plate It. The end of this latch plate is disposed in the path of a spring 1 fixed at th'e end of bi- -metallic strip c andprovided with a perforation i', shown more clearly in Figure la, in which, the end of latch platen engages when contact v spring at and bimetallic strip c are latched together and contacts e and I are closed. The fixedend of strip 0 is connected by way-of a conducting strip 1 to binding post k of the switch, ,and'thef fixed end of contact spring a is connected by way of a conducting strip m to theother binding post n of the switch. A protecting capp, which is held in place by means of a handscrew, encloses the entire switch mechanism.

I overload condition should when the switch is inclosed position, as in Figure 1-, the bimetallic strip c is heated and thereby bends at its free end toward base a, Thereby'both'the strip andcon 40 tact spring d first travel together downwardly;

but in doing so, the latching elements It and i shift in the direction of the longitudinal axis of springid relatively to oneanother, and when strip 0 has bent down for enough,'latch It isjdisengaged from spring i, and contact spring it,

being now free, quickly snaps upwardlydue to a normal upward bentprovided near its mounting point as shown in'lhgure 2. The latch mechanism disengages during the downward bending '50 ofstripcduetothespacingbetweenstripcand.

which is directed toward the side of bindinflpost n and thus away from" spring 1, while the free end of spring i lithe same time follows a circular path which is" directed toward binding postok and thus away from latch h. As soon as so the two contact elements have followed a sufficient distance in these two paths, they slide apart and the latch mechanism is opened and the 'contactarms fly apartr The greater the Y diflerence in the radii on which the two contact 6|! arms move, the sooner the mechanism will be unlatched. As soon as the bimetallic strip has cooled, it reassumes its straightposition shown I in Figures 1 and 2, but contact spring (I remains, in its elevated position'shown in Figure 2. In

order to reclose and relatch the contacts, it is necessary in this modification to loosen the hold-- ing screw 0 of casing p'to'remove the casing and to-depress spring at until latch h r'eensases 76 The modification shownln 3, and

This arrangement operates as follows. 1! an is distinguished from that shown in Figures 1 and 2 by the additional provision of a resetting mechanism which can be operated from outside of the casing but which is constructed so that it does not interfere with the free operation of l the automatic cut-out mechanism and so that in case it is accidentally operated in such manner as would cause such interference, the circuit is opened thereby. In this modification, the thermostatic releasing mechanism comprising the 1 spring d, bimetallic strip 0, contacts e and f and the latch mechanism It, i are the same and function in the same manner as described with reference to Figures 1 and 2. In this case the bimetallic strip c is connected to'binding post'n. l5 The contact spring d, separated from strip c by means of the insulating block b, is connected to binding post It by way of auxiliary contacts a, t. Contact s is mounted on a contact spring r connected directly to binding'post k, and contact t is mounted at the end of spring it which leads to the fixed end of contact spring d where it is held together with spring d? on block b. This auxiliary contact, which is normally closed when the automatic switch isclosed, is controlled by meansof a press button a mounted in casing p, held by screw 0 to base plate a, so that when this button is depressed. contacts a, t are opened. This button has a downward extension in which,

when/the button is depressed, engages the in sulating strip a of spring d.-- When the autoreclose' and relatch the switch mechanism b0 depressing button 9, contact spring it approaches I the bimetallic strip c,jbut before the switch con- 0 ,tactseandfcanbeclosed,theport ionw' oftbe contact button carries the auxiliary contact t of spring it .away from contact s, so that when the depression of button 0 is continued and switch contacts e and f are closed and the latch h en- 48* gages spring i and locks contacts e and f together, auxiliary contacts a and t are still open,

and thus the circuit is It can be closed only when button 12 is released so that prin it carries auxiliary contact t back into con- 50 tactwithe. ItwillbeseenfromthisarrI-ngement that if now with all contacts closed and the switchin operation, as shown in Figure 3, anattempt should be made accidentally towder I press button 0, which would interfere with the so free opening of the latched switch, should the circuit condition at that moment call for an ,opening, auxiliary contacts-s, t will be opened and,the. circuit will be interrupted thereby.

The modification shown in Figures 8, 'l and two is distinguished from the switch forms shown'in the previously described figures by the following arrangement. In this case the bimetallic strip c with itscontact e and spring t at the free "end,; isfixed on the casing p, which for this 'purll pose may be made of any suitable insulating. material. @ownwardly spaced from the fixed end of strip 0 is fixed the en'd of contact spring d.

Otherwise these elements are shaped and function in the same manner as described with ref- 7.

arouse -d and strip become connected respectively-with the binding posts 11. and it when casing p is attached to the base-plate a, as shown in Figure "l, by means of latch springs and latches a, 1:, ll, 1!.

The switch is shown in Figure 7 in closed position. If new the switch responds due to an overload, the two switch'contacts e and-j become unlatched and fly apart and assume the cations.

position shown in Figure 6. When this has occurred and in order to reclose the switch, the operator removes casing p from base plate :1,

whereby he automatically disconnects the entire 1 switch from binding posts k' and 11.. He now can reclose and relatch the contacts e and f with his finger. Only in relocking cover p on base plate a by means of latch springs 22, a: can the circuit eventually be closed.

My invention is not limited to the particular constructive details shown in the three modifi- For simplicity sake, for instance only a single pole switch has been shown. Itis quite obvious that a number 01 such switches may be I easily mounted side by side, since they are very narrow, as may be seen from Figure 8, and thus any number of poles of a circuit may be accommodated and be automatically interrupted. Fir instance, four of such automatic switches for four conductors may be accommodated within the compass occupied by prior art automatic switches capable of interrupting only asingle line. I

Moreover, the construction of the switch according to my invention is not limited to the particular manner of latching the two contactcarrying elements c and d together. Thus, for instance, the latch plate need not be located on an extension of the contact spring d but on an extension of the bimetallic strip c. In this case a latch plate is provided at the free end of the bimetallic strip and an angularly bent spring is provided at the free end 01' the contact spring (I; in other words, the elements i and h, for instance in Figures 1 and 2, may be reversed, the spring i may be mounted on the insulating piece g and the latch It may be mounted at the end of bimetallic strip c. Also the latching point may be located intermediate the ends of the two contact-carrying elements 0 and d, in which case angularly shaped springs may be attached to the free ends of the-contact-c'arrying elements 0 and, d as latching elementsi A modification combining 'the foregoing modifications is shown in Figure 9. The bimetallic strip 0 carries an insulating piece a to which a latch h is secured, the latch and the coasting spring being so shaped that the latching point liesbetween' strip 0 and spring d,

Furthermore, "referring for instanceto'rigures 1, and 2, the unlatching may occur earlier or later during the bending process of the bimetallic strip according to the relative position oil-the.

latching elements to the points at which the'contact-carrying elements 0 and d are fixed. For

instance if in Figure 1 the latch plate h instead of being fixed at the upper side of. insulatin piece 9 is fixed on its underside, as it; is illustrated in'Figure 100, the automatic cut-'out will respond earlier at the same loadthan it would respond with'the arrangement shown in Figures 1 and 2. On the other hand, if the latch plate It should be raised higher above insulating piece a,- in otherwords it the latching point shouidbe elein' the manufacture of the switch, its constitu-- ent 'parts' may all be the same, but for different overloads or tor-different times of response, spacingblocks of different heights may be used in order to determine the desired point of response. Accordingly, the spacing blocks b, b and b"- in Figures 1, 10a and 10b are distinguished from one another by different heights.

Also the time of response may be varied by increasing or decreasing, as the case may be, the

relative lengths of the two contact-carrying elements 0 and d. This will. either increase or decrease the diflerence in the radii of the circular paths through which the free ends of these elements move and bring about an earlier or later response of the switch from the time when the overload' manifests itself in heating the strip 0. An example embodying the last-mentioned modification is represented by Figures 11a. and 11b. The bimetallic strip 0 and the spring (1 shown in Figure 11a are arranged similarly to Figure 1, except that the spacing block b allows exchanging 01' spring 11' by a shorter spring d" as shown in Figure 11b, which eifects an earlier response to a given overload.

I claim: 1. A thermostatically released cut-out switch having two switch contacts and a contact spring carrying one of the switch contacts and. tending to move its contact into open position, and a thermostatically operable bimetallic strip disposed to control the other switch contact, said spring and said strip element each being fixed at one end and spaced a given distance apart one from and above the other, and means at the free ends of said elements for normally latching them together in contact closing position, whereby clue to the relative spacing of said elements a relative motion of the latched ends in axial and opposite directions is produced; when the bimetallic strip is thermostatically bent into its own contact opening position against the opening tendency of said contact spring, by which motion the element ends are unlatched and the spring is permitted to move its contact away from said strip into its own open contact position.

2. A thermostatically released cut-out switch having two switch contacts and a contact spring carrying one of the switch contacts and tending to move' its contact into open position, and a thermostatically operable bimetallic strip disposed to control the other switch contact, said spring and said strip element each being fixed at one end and spaced a given distance apart one from and above the other in the same plane, a latch spring fixed at the end of said strip and extending substantially at right angles to it and across said contact spring when in closing position, and a latch fixed at the end of said contact spring and arranged to engage said latch spring in contact closing position for normally latchingthe strip and the contact spring together in contact closing position, whereby due to the relative spacing of said contact spring and said strip a relative motion of the latched ends in opposite directions is produced when the bimetallic strip is thermostatically bent into its own con- 1 tact opening position against the opening tend-'- ency of said contact spring, by which motion 7 the latched ends are unlatched and the contact spring is permitted to move its contact away from said strip into its own open contact position.

3. A thermostatically released cut-out switch having a base plate and two binding posts on said plate, and a casing fitted onto said plate and enclosing said posts, said casing containing two switch contacts and having mounted in its interior a contact spring, carrying one of said switch contacts and tending to move its contact into open position, and a thermostatically operable bimetallic strip disposed to control the other switch contact, said spring and said strip element each being fixed at one end to said casing and spaced a given distance apart one from and above the other in the same plane, and meanssaid stripinto its own open contact position, and

' said period.

yielding locking contact elements "connected respectively to said binding posts and to the fixed ends of said contact spring and said strip for 7 connecting said spring and said strip respectively to said binding posts and for locking said casing to said base plate. a

4. A thermostatically released cut-out switch having a base member, two switch contacts, an overload-responsive bimetallic strip (11890566150 control one of said contacts, said strip having one end firmly secured to said base,'a spring memspring member to travel along with said strip during a releasing period within which said ends eflect a longitudinal ent relative to each other, and means for exchangeably securing the other end of said spring member to said base, said means being designed to selectively accommodate a diflerent spring member in a diluent spacial relation to said strip in order to vary wnmussmm. "so 

